COBE sky map

This map of the ancient sky shows the minute variations in the
microwave background discovered by the team led by Lawrence Berkeley
Laboratory astrophysicist George Smoot. As seen in the map, vast
regions of space have minute variations in temperature. Over billions
of years, gravity magnified these small differences into the clusters
of galaxies we observe today. Displayed horizontally across the middle
of the map is the Milky Way galaxy.

The image, a 360-degree map of
the whole sky, shows the relic radiation from the Big Bang. The map
was derived from one year of data taken by the Differential Microwave
Radiometers onboard NASA's Cosmic Background Explorer satellite. Using
Galactic coordinates, the map shows the plane of the Milky Way galaxy
horizontally and the center of our galaxy at its center.

The colors
represent temperature variations with red indicating regions that are a
hundredth of a percent warmer and blue indicating regions that are a
hundredth of a percent cooler than the average temperature of 2.7
degrees above absolute zero. Away from the plane of the galaxy, many of
the features shown are noise.

According to the "inflationary Big
Bang" theory on the birth of the universe, as the universe began to
expand in the instant after the primeval explosion, its energy density
was nearly uniform in all directions save for very small amplitude
variations. Gravity working over billions of years magnified these
variations, causing galaxies to form and to cluster in the sky. These
galaxy clustering patterns, predicted by theory, have been seen for
several years, but this study provides the first evidence for the
corresponding fluctuations in the background radiation in the sky.
Thus, a 15-billion-year-old fossil of the conditions of the universe
has been detected and measured for the first time.

Computer analyses show that the pattern of the fluctuations agrees
with the predictions from the inflationary Big Bang scenario. The
amplitudes of the observed
fluctuations are consistent with theories that explain the birth and
growth of galaxies using large amounts of an enigmatic material called
"dark matter." According to these theories, most of the universe is
composed of material that we not only know very little about, but that
has never been seen directly.